CN105556588B

CN105556588B - Constant tension device

Info

Publication number: CN105556588B
Application number: CN201480048625.3A
Authority: CN
Inventors: 克斯摩·莱尔斯
Original assignee: INTUNE TECHNOLOGIES LLC
Current assignee: INTUNE TECHNOLOGIES LLC
Priority date: 2013-09-03
Filing date: 2014-09-03
Publication date: 2020-02-21
Anticipated expiration: 2034-09-03
Also published as: WO2015034952A1; US9318081B2; JP2016534405A; JP6461156B2; CN105556588A; US20160225352A1; US9613600B2; US20150059550A1; EP3042373B1; EP3042373A4; JP2019070442A; EP3042373A1; JP6823041B2

Abstract

The support is configured to support a wire or string, such as a musical string of a stringed instrument, and to apply a constant or near constant tension to the wire or string. The wire is attached to an axially moving carrier. One or more springs operate between the carrier and a point fixed relative to the carrier and apply a lateral spring force to the carrier. The spring angle is defined between a line normal to the axis and a line of action of each spring. The transverse spring force may have an axial force component and the axial spring rate is a function of the spring angle. The carrier may be positioned such that the axial spring rate is zero, negative, or positive. The main spring may exert a main force directed coaxially with the wire. If the wire varies in length, the principal force will vary accordingly, as will the axial force component. The transverse spring may be selected such that the axial force component of the transverse spring approximates the change in force applied by the main spring such that the axial force applied to the carrier and wire remains substantially constant.

Description

Constant tension device

Cross Reference to Related Applications

This application is based on and claims the benefit of U.S. application No. 61/873,295 filed on 9/3/2013 and U.S. application No. 61/875,593 filed on 9/2013, both of which are hereby incorporated by reference in their entirety.

Background

The present disclosure relates to the field of devices for applying tension to a filament or string, and more particularly to devices that will maintain such tension constant or near constant as the filament is stretched or shortened over a limited range.

Various products and applications benefit from maintaining the wire or string at a near constant, predictable tension over time and under various environmental conditions. Notably, stringed musical instruments create music by vibrating strings held under tension. If the string is under the correct tension for a given instrument, it will vibrate at the desired frequency corresponding to the desired note. However, music strings tend to stretch or shorten over time and/or due to environmental factors such as temperature, humidity, or the like. Such stretching or shortening typically results in a change in tension in the string, and the string thus vibrates at a frequency different from the desired frequency. This may cause the string to be pitched, emitting a note that is acoustically different from the desired note. Conventional string instruments tend to pitch quickly and musicians often find themselves spending a great deal of time adjusting their instruments, even during a performance.

The appearance that a musician's instrument looks is often seen as an expression of an artist, and thus the musician tends to expect that the component parts of his instrument are unobtrusive so as not to dominate the appearance. Furthermore, some instruments (particularly acoustic instruments) may be sensitive to component parts placed in certain parts of the instrument. Furthermore, the component parts should avoid possible interference with the musician while playing.

SUMMARY

There is a need in the art for a method and apparatus for mounting strings of a stringed musical instrument in a manner such that the strings remain under near constant tension even if the strings stretch or shorten over time and/or due to environmental factors.

There is also a need in the art for a method and apparatus that is relatively small and easy to install in certain stringed musical instruments without substantially changing the sound of the instrument, changing its appearance, or interfering with playability.

According to one embodiment, the present invention provides a constant tension device. The device includes a primary spring attached to the carrier for exerting a primary spring force. The primary spring force applied to the carrier varies as a first function as the carrier moves along an axis relative to the primary spring. A wire or string is attached to the carrier and extends along the axis such that an axial force applied to the carrier is applied to the wire or string. A secondary spring has a first end attached to the carrier for applying a secondary spring force to the carrier. The secondary spring force is directed transverse to the axis and has an axial component applied to the carrier in a direction along the axis. The secondary spring force is configured such that an axial component of the secondary spring force varies according to a second function as the carrier moves along the axis relative to the primary spring. The net axial force applied to the carrier comprises the sum of the axial component of the secondary spring force and the primary spring force.

In one such embodiment, the stringed musical instrument comprises such a constant tension device, and the wire or string is a musical string having a first end attached to the carrier and a second end fixed relative to the carrier. The secondary spring is selected such that an axial component of the secondary spring force varies as a function of the secondary spring rate as the carrier moves longitudinally along the axis, and the secondary spring rate function approximates and opposes the primary spring rate function such that the net axial force applied to the carrier stays within about 1.2% of a preferred tension per millimeter of longitudinal movement. In another embodiment, the secondary spring is selected such that an axial component of the secondary spring force has a magnitude that approximates the change in primary spring force applied to the carrier as the carrier moves longitudinally along the axis such that the net axial force applied to the carrier stays within about 0.6% of a preferred tension force per millimeter of longitudinal movement.

In another embodiment, the second end of the secondary spring is fixed relative to the carrier, and a secondary spring angle is defined between a line normal to the axis and a line of action of the secondary spring. The carrier has an operating range defined as a distance along the axis between opposing first and second axial positions, the carrier being between the first and second axial positions. Some embodiments further comprise a first stop at the first axial position of the operating range that prevents the carrier from moving beyond the first axial position in a first direction. Some such embodiments further comprise a second stop at the second axial position of the operating range that prevents the carrier from moving beyond the second axial position in a second direction.

In other embodiments, the operating range corresponds to a change in assist spring angle of up to 10 °.

In one embodiment, the secondary spring force is directed in a direction normal to the axis at a point within the operating range. In further embodiments, the operating range is defined within a range in which the secondary spring angle is between ± 5 °.

In some embodiments, a guitar includes such a constant tension device mounted to one of a head or a bridge of the guitar. A guitar string has a first end attached to the carrier and a second end attached to the other of the head and bridge of the guitar. The tension in the guitar string is equal to the axial force applied to the carrier.

In some such embodiments, the carrier is movable to a position at which the guitar string is held at a perfect tuning tension, and as the guitar string elongates, the axial force applied to the carrier by the primary spring decreases and the axial component of the force applied to the carrier by the secondary spring in the direction the carrier moves as the guitar string elongates increases.

In another embodiment of the guitar, the second end of the secondary spring is fixed relative to the carrier, and a secondary spring angle is defined between a line normal to the axis and a line of action of the secondary spring. The carrier has an operating range defined as a distance along the axis corresponding to an auxiliary spring angular variation of up to 10 °. The main spring has a main spring rate and the secondary spring has an axial spring rate component opposite the main spring rate such that a change in tension in the guitar string over the operating range corresponds to a range of frequencies of 10 cents or less.

In a further embodiment, the secondary spring comprises a pair of springs acting on opposite sides of the carrier, the second end of the secondary spring being fixed relative to the carrier. In some such embodiments, the secondary spring may be rigidly connected to the carrier and to a fixed secondary spring mount.

In some embodiments, the secondary spring comprises a flat sheet that deflects in compression. In a further embodiment, the flat sheet is rigidly connected to the connector and to a fixed secondary spring mount. In a further embodiment, the plurality of flat sheets are spaced apart from each other.

In yet a further embodiment, the pair of springs includes a deflection rod.

Some such embodiments further comprise a connector between each deflection bar and the carrier. In some embodiments, the connector comprises an elongate rod. In other embodiments, the connector comprises a ball bearing.

According to yet another embodiment, a constant tension device is provided. The apparatus comprises a carrier configured to be movable along an axis and a wire or string attached to the carrier and extending along the axis such that an axial force applied to the carrier is transmitted to the wire or string. The target tension is defined as the desired tension of the wire or string. A spring has a first end attached to the carrier and a second end attached to a spring mount, the second end being fixed relative to the carrier such that the spring applies a spring force to the carrier. A spring angle is defined between a line normal to the axis and a line of action of the spring. The spring force is directed transverse to the axis and has an axial force component and an axial spring rate that is transmitted to the carrier in a direction along the axis. The spring is selected such that the axial force component is equal to the target tension when the spring angle is a zero stiffness angle at which an axial spring stiffness of the spring is zero.

In another embodiment, the axial spring rate is one of negative or positive when the spring angle is greater than a zero rate angle, and the axial spring rate is the other of negative or positive when the spring angle is less than the zero rate angle.

Brief description of the drawings

FIG. 1A shows a schematic representation of a spring arrangement;

FIG. 1B shows the spring arrangement of FIG. 1A in a configuration in which the strings have been stretched;

FIG. 2A shows a schematic representation of a spring arrangement according to one embodiment;

FIG. 2B shows the spring arrangement of FIG. 2A in a configuration in which the strings have been stretched;

3-5 show schematic representations of a spring arrangement according to another embodiment, shown in three positions;

FIG. 6 shows a schematic representation of another spring arrangement according to yet another embodiment;

FIG. 7 shows a schematic representation of yet another spring arrangement according to another embodiment;

FIGS. 8A and 8B show a schematic representation of a spring arrangement according to another embodiment, shown in two positions;

FIGS. 9A and 9B show a schematic representation of another embodiment of a spring arrangement shown in two positions;

FIG. 10 is a schematic representation of features that may be employed in at least some of the embodiments described herein;

FIG. 11 is a close-up schematic view of a stop feature according to one embodiment and shown in the context of a portion of the embodiment of FIG. 9;

FIG. 12 is a schematic representation of a spring arrangement configured in accordance with yet another embodiment;

FIG. 13 is a schematic representation of a spring arrangement configured in accordance with another embodiment;

FIG. 14 shows an embodiment of a tension device that employs features as in the embodiment shown in FIG. 12;

FIG. 15 shows a schematic representation of a bass guitar employing a tensioning device on the guitar's head;

FIG. 16 is a schematic representation of a spring arrangement configured in accordance with further embodiments; and

fig. 17 shows a perspective schematic view of an embodiment of a tension device employing features as in the embodiment shown in fig. 16.

Description of the invention

The following description provides examples illustrating aspects of the invention employed in various embodiments. It is to be understood that there may be embodiments that are not explicitly discussed herein, but that may employ one or more of the principles described herein. Furthermore, these principles are discussed primarily in the context of stringed musical instruments. However, it should be understood that the principles described herein may have other applications, such as sporting goods, industrial, and/or construction applications in which it may be desirable to apply a near constant force to an article that is movable within an operating range and/or that employs a spring arrangement that may exhibit a positive spring rate.

The present disclosure describes embodiments of an apparatus that can apply a near constant tension to a string, wire, or the like, even when the length of the string, wire, or the like varies over a range of distances. Notably, applicant's U.S. patent No. 7,855,440 (which is incorporated herein by reference in its entirety) teaches similar but different principles for achieving near constant tension in a wire or string as it stretches and/or shortens.

Referring first to FIG. 1A, a spring-based tension device 30 includes a wire 32 having a fixed end 34 and a movable end 36, and a main spring 40 having a fixed end 42 and a movable end 44. The fixed end 34 of the wire 32 is mounted on a fixed wire mount 38; the fixed end 42 of the main spring 40 is mounted on a fixed spring mount 48. The main spring 40 has a spring constant k. The movable ends of the wire 32 and the main spring 40 are both attached at the carrier 50 (or attachment point) such that the main spring 40 and the wire 32 are coaxial. The main spring 40 pulls the wire 32 such that the force Fp in the main spring 40 is the same as the tension Tw in the wire. In this embodiment, the preferable tension is Tp. In fig. 1A, Fp ═ Tw ═ Tp.

Over time, the filaments 32 may stretch or shorten. Fig. 1B shows this because the filaments 32 have been stretched an axial distance x. Since spring 40 obeys hooke's law, the force in spring 40 decreases by-kx, causing a corresponding change in the tension Tw in the wire. Therefore, Fp ═ Tw ═ Tp-kx. Thus, the tension in the wire 32 is no longer at the preferred tension Tp. Notably, hooke's law (F ═ -kx) is a linear function.

Fig. 2A-2B illustrate another embodiment of a spring-based tension device 30 for maintaining the tension in the wire 32 at or near a preferred tension Tp. The assist spring 60 has a fixed end 62 and a forward movable end. Fixed end 62 is attached to secondary spring mount 68. The movable end 64 of the secondary spring 60 is attached to the movable ends 36, 44 of the main spring 40 and the wire 32 at the carrier 50. As shown in fig. 2A, the secondary spring 60 exerts a force Fs, which in the initial position shown in fig. 2A is directed orthogonally to the force Fp applied to the wire by the primary spring 60. And II, performing secondary treatment. Preferably the carrier 50 is constrained to move only along a path coaxial with the main spring 40 and the wire 32. Since Fs is directed orthogonal to the attachment point in fig. 2A, Fs has a vector force component Fsa of zero (0) along the axis. Thus, the assist spring force Fs does not affect Tw.

Referring to fig. 2B, as discussed above in connection with fig. 1B, over time, the wire 32 may stretch, resulting in a reduction in the primary force Fp applied to the wire 32 by the primary spring 40 (by kx) — however, as the carrier 50 moves along the axis a distance x, the secondary spring 60 rotates about its fixed end 62 by an angle α. the secondary force Fs is no longer directed orthogonal to the axis but has an axial vector component (Fsa) determined by the equation Fs (sin α). thus, the tension in the wire is calculated as Tw Tp-kx + Fs (sin α). it is noted that Fsa may also be determined by Fs (cos θ), such that Tw Tp-kx + Fs (cos θ).

At relatively low angles of α, such as about 0-20 °, more preferably 0-15 °, still more preferably 0-10 °, and most preferably 0-5, sin α is a substantially linear function, as described above, -kx is a completely linear function in which the primary spring rate k is constant and which is negative, -therefore, at such relatively low angles of α, the secondary spring force Fs may be selected such that, over the operating range of deflection (x), the value of the function k(s) x is similar to Fs (sin α), and the secondary axial spring rate k(s) varies with α and the spring rate function is positive-as such, over the operating range shown in fig. 2B, as the wire 32 elongates, the axial force component Fsa by the primary spring 40 Fp decreases, but the axial force component Fsa by the secondary spring increases correspondingly, and directed in the same axial direction as the primary force, the result of the total tension on the wire being maintained at the preferred tension Tp or close to the preferred axial force component applied by the secondary spring, Tp 2, and if the result of the applied force component applied by the secondary spring is a negative tensile force f, Tp, f, and f, a, f.

Table 1 below provides a spreadsheet demonstrating a real-world scenario with the performance of one embodiment of the structure as depicted in fig. 2A-2B. In the scenario depicted in table 1, the main spring 40 (spring 1), the auxiliary spring 60 (spring 2), and the chord 32 are attached, as represented in fig. 2A-2B. The main spring (spring 1) has a spring rate of 64 pounds per inch (k 1). The helper spring (spring 2) is in compression and has a spring rate of 10 pounds per inch (k 2). The travel range of the attachment point (carrier 50) is 0.0625 inches. In this embodiment, the secondary spring (spring 2) has an initial length y of 0.3 inches and is compressed to have an initial tension (Fs) of 19.7 pounds. In this scenario, the initial position of the secondary spring 60 is orthogonal to the primary spring 40.

TABLE 1

In the scenario depicted in table 1, the tension Fp is initially in the main spring (spring 1), and thus the preferred tension Tp in the wire is 10 pounds, and the initial length L1 of the main spring 40 is 1.4 inches. The spreadsheet simulates an application such as a guitar in which a spring applies tension to the guitar string and the guitar string stretches over time (here within a 0.0625 inch travel range). The spreadsheet shows the state of the springs and the tension in the wire/guitar string at each point along the 0.0625 travel range.

As shown in FIGS. 2A-2B and represented in Table 1, as the string 32 stretches, the carrier 50 and associated attachment point move, with the result that the length of the primary spring 40 (spring 1) decreases by a distance x and the primary force Fp decreases accordingly, however, the secondary spring 60 (spring 2) rotates, thereby increasing the axially directed component force Fsa, calculated as Fscos θ or Fssin α. it is noteworthy that the length L2 of spring 2 will vary slightly with this rotation (calculated as ((y ^2+ x ^2) ^ L/2), and therefore Fs will vary slightly due to the spring stiffness of spring 2.

In the scenario shown in table 1, the secondary spring 60 (spring 2) rotates almost 12 degrees within 0.0625 inches of chord stretch, and the total tension (Tw) in the wire changes by at most about 0.4% from the preferred (initial) tension Tp. Such a change will result in minimal, if any, audible changes in the guitar's tuning.

It will be appreciated that various lengths, spring rates, etc. may be selected for the primary and secondary springs in order to vary the particular result, but the principle remains that the secondary spring is selected to approximate the linear change in tension exerted by the primary spring as it moves linearly, and that the secondary spring (or at least the line of action of the secondary spring) changes such that the rate of change of the axially directed component force approximately cancels the rate of change of the primary spring force.

Referring next to fig. 3, in another embodiment, opposing spring mounts 68 are fixed relative to each other and are spaced apart from each other by a width w. A pair of identical springs 60 are provided, with a fixed end 62 of each spring being attached to a respective one of fixed spring mounts 68 and a forward movable end being attached to carrier 50 configured for linear translation along axis a. As shown, the springs 60 are preferably arranged symmetrically about this axis. Wires 32 or the like may be attached to carrier 50.

In the embodiment shown in fig. 3, each spring 60 has an angle α relative to a line normal to axis a. in fig. 3, α is 60 °. with additional reference to fig. 4 and 5, and also with reference to table 2 below, as carrier 50 moves along this axis, angle α decreases, the length of springs 60 and the axial force component Fsa of each spring also decreases as the springs are placed in compression.

In table 2 below, an example is presented in which spring 60 is initially arranged such that α is 60 ° and the spring has a resting length of 2.0 inches the example spring has a spring rate k of 90 lbs/inch and the width w between the fixed spring mounts 68 is 2.0 inches such that each fixed spring mount is 1.0 inch from the axis table 2 shows how various aspects of the arrangement change as demonstrated in fig. 3-5 as carrier 50 moves linearly along the axis in particular as α decreases the length L of each spring decreases and each spring is placed in compression, applying a spring force Fs. which can be resolved into components including an axial component Fsa of force, α changes by a corresponding incremental change in the axial distance moved by carrier 50 for each degree of decrease the axial force Fsa divided by the axial incremental distance represents the axial spring rate ka. moving along the spring at that point and thus as shown in table 2 the axial spring rate α changes.

TABLE 2

Referring next specifically to fig. 4 and table 2, when α is approximately 37 °, the incremental axial spring rate transitions from a negative spring rate to a positive spring rate, hi addition, referring to fig. 5 and table 2, the incremental spring rate at an angle approaching α ° to 0 ° is nearly constant and, in the illustrated embodiment, is positive, more specifically, the spring rate is generally constant in the region around α ° to 0 ° from approximately α ° to α ° to-5 °.

Referring next to fig. 6, in another embodiment, in a manner similar to the embodiment of fig. 2, an axially directed primary spring 40 is attached to the carrier 50 and adapted to provide a primary spring force Fp to the wire 32, the wire 32 also being attached to the carrier 50 in fig. 6, an opposite identical secondary spring 60 is arranged as the spring 60 in fig. 3-5, in the present embodiment, the primary spring 40 obeys hooke's law and thus has a constant spring rate k, as shown, the secondary spring 60 is disposed within a range of α ± 0 °,5 °, wherein the axial component Fsa of the force of the secondary spring 60 is a function of sin α which is a nearly linear function at very small angles, such as α ± 0 °,5 ° as shown, in the preferred embodiment, the secondary spring 60 may be selected to have a spring constant such that its axial force component Fsa generally follows and compensates for the linear force p as the wire 32 (or musical string, in some embodiments) moves axially as the primary shaft p as time or as the tension or the wire 32 is stretched or shortened, such that the linear force decreases within a range of 3975 ° as approximately equal to the operating range of ± 0 °, 10 °, or even shorter, preferably 10 °.

With continued reference to fig. 6 and with reference again to table 2, in a preferred embodiment, the combined total spring rate of the two secondary springs 60 approaches 90 lbs./inch due to the spring rate of each secondary spring 60 at α and around α at 0 deg. in one such embodiment, the primary spring 40 is selected to have a spring rate of-180 lbs./inch so that in an operating range of about α at 0 deg. relative to the opening, the primary spring 40 has a spring rate of about-180 lbs./inch in tension while the secondary springs combine to provide an axial spring rate of compression of about 180 lbs./inch then the combined spring rate approaches zero, which results in a change in the force exerted by the tension device 30 approaching zero over an operating range of about α at 0 deg..

More specifically, in the embodiment depicted in fig. 6 and table 2, as the carrier 50 moves from α ° to α ° at 1 °, it moves axially 0.017455 inches, thus the tension applied by the primary spring 40 decreases (180 lb/in) (0.017455 in) at 3.1419 lbs. however, the axial component Fsa of the force provided by the two secondary springs 60 is 2(1.57048 lb) at 3.1410 lbs. thus, as the carrier 50 moves from α ° to α ° at 1 °, the net change in tension is only 0.0009 lbs. additionally referring to table 3, the net axial spring rate ka for α ° 0 ± 5 ° is calculated by adding the combined axial spring rate of the secondary springs 60 to the primary spring rate (here 180 lb/in).

Alpha (degree)	Net spring rate
		5	-4.9630
4	-3.3328
		3	-2.0244
2	-1.0407
		1	-0.3837
0	-0.0548
		-1	-0.0548
-2	-0.3837
		-3	-1.0407
-4	-2.0244
		-5	-3.3328

TABLE 3

As seen in table 3, the net axial rebound spring rate ka averages about-1.15 lbs/in the range of-4 ° to 4 ° at α, about-1.37 lbs/in the range of-5 ° to 4 ° at α, and about-1.69 lbs/in the range of-5 ° to 5 ° at α.

Referring next to fig. 7, in another embodiment, the operating range of the spring-based tension device 30 may be arranged to span a region of zero spring rate where the spring rate transitions from a negative spring rate to a positive spring rate because the magnitude of the spring rate reverses within the range, the net average spring rate may be limited within a desired range.

Referring next to fig. 8A, another embodiment of a spring tension structure 70 configured in accordance with one embodiment follows a theoretical characteristic similar to that schematically illustrated in fig. 6.

As shown in fig. 8A, main spring 40 is attached at a fixed end to fixed mount 38. The movable end 44 of the main spring 40 is attached to a carrier 50 that is preferably constrained to move axially. The carrier 50, in turn, is attached to the wire or string 32 such that the main spring 40 is coaxially aligned with the string 32 and applies tension to the string 32, and the change in tension provided by the main spring 40 varies according to the function-kx. In the present embodiment, the secondary spring assembly includes a pair of oppositely disposed cantilevered rods (rod springs) 72, with the cantilevered rods (rod springs) 72 acting as linear flexure springs. Each rod spring 72 is connected to the carrier 50 via a forward connector rod having opposed knife-edge ends 76 that are received into respective knife-edge receivers 28 formed in the carrier 50 and the rod springs 72. The knife edge end 76 and the receiver 78 form an interface 80 on either end to minimize rotational friction as the carrier 50 moves relative to the lever spring 72 and the connector lever 74 correspondingly rotates.

Fig. 8A depicts the device 70 in an arrangement where α is 0 ° in operation, as the wire or string 32 elongates (see fig. 8B), the carrier 50 moves axially (e.g., distance x) and the connector 74 rotates accordingly, and in the manner discussed above, the secondary spring force Fs provided by the rod springs 72 develops a non-zero axial component Fsa, each rod spring 72 providing half of this force, and transmitting the force Fsa to the carrier through the connector rod 74.

9A-9B depict another embodiment 90 in which the lever spring 92 provides a secondary force, in FIGS. 9A-9B the lever spring 92 has a curved surface 96 (e.g., a semi-circular shaped surface) at a joint 100 and the carrier 50 also has a curved surface 98 (e.g., a semi-circular shaped surface) at a carrier joint 100. A bearing 102 (e.g., a spherical ball bearing) is interposed between each lever spring and the carrier's curved engagement surfaces 96, 98. the operation of this embodiment is similar to the embodiment of FIGS. 6 and 8. however, as the carrier 50 moves axially, the ball bearings 102 rotate on the engagement surfaces 96, 98 with very little friction.

In some embodiments, the

curved surfaces

96, 98 can be arcs of about a fixed radius of curvature in other embodiments, the curved surfaces can have a radius of curvature that varies along their length to produce a camming effect.

The carrier 50 employed in this or other embodiments disclosed herein may be supported in any desired manner. In some preferred embodiments, it is suspended above the surface, held in place by tension provided by the main spring and borne by the attached wire or string. In other embodiments, it slides over the surface. In other embodiments, it is supported on the surface by linear bearings.

In a preferred embodiment, and with reference next to FIG. 10, it is preferred that the fixed end of the main spring 40 can be selectively moved to vary the initial tension/initial main spring length. In the illustrated embodiment, the tuning pin or knob 106 is supported by a pin frame 108 and is threadably attached to a seat carrier 110 carrying the main spring fixed seat 48. As the tuning pin 106 rotates, the main spring fixed end support 48 is moved. The carrier 110 also preferably moves axially, and thus the main spring is elongated, providing more tension. Preferably, the wire or string may also be tensioned so that the carrier is moved to a position where the tension is provided entirely by the main spring.

With additional reference to fig. 11, the stop mechanism 120 includes first and second translation limiters 122 (or stops) that may be positioned to prevent the carrier 50 from moving axially outside of a desired operating range. In some embodiments, the stop mechanism is attached to a frame or other support that can support an associated tension device.

In some guitar-based embodiments, the user may tension the string via tuning pin 106 sufficiently that carrier 50 is immediately adjacent second stop 122 (on the string side of the carrier). In this way, if the user desires to "bend" the note during play, the carrier 50 will engage the second detent, preventing further movement of the carrier 50 to compensate for the user pulling the string 32, and thereby allowing the user to increase the tension in the string, resulting in a "bent" note.

Referring next to fig. 12, another embodiment is schematically represented in which the primary spring 40, which is coaxial with the string 32, comprises a coil spring held in tension and connected to the string 32 via a carrier 50 configured to move linearly along an axis a. the secondary spring 130 is configured to comprise a planar piece of spring steel having a length greater than the width w between the spring mounts 68 to which the planar spring 130 is attached. the center of the planar spring 130 is also attached to the carrier 50 and the planar spring 130 is compressed such that it fits within the width of the device as shown, due to such compression, the planar piece 130 is deflected into two symmetrical curves, one on each side of the axis as shown in fig. 12, each curve providing a secondary spring force Fs. in compression and directed transverse to the axis in the illustrated embodiment, where the secondary spring force is directed in the direction of α ═ 0 °, as the spring elongates or shortens, the carrier 50 will move axially and the secondary spring will employ an axial component Fsa that will at least partially compensate for the axial change in the spring force applied by the primary spring 40 as discussed above.

Referring next to fig. 13, in another embodiment, a planar spring leaf 140 of spring steel may be used to configure the tension device, with the secondary spring force directed in a direction generally corresponding to the deflection angle corresponding to the zero spring rate position. As discussed above in connection with fig. 7, the main spring is not necessary in embodiments that operate around the zero spring rate position.

Referring next to fig. 14, another embodiment is shown in which a tension device 160 is configured similar to the configuration of fig. 12, except that a plurality of deflection flats 130 are provided to generally provide the desired assist spring force Fs. In the illustrated embodiment, the fixed spring mount 68 includes spacers 162 to keep adjacent spring steel plates 130 spaced apart from each other, but held fixed in clamps 164 of the mount 68. Similarly, in the present embodiment, the carrier 50 is elongated and includes several spacers 162 that maintain the space between adjacent spring steel sheets 130. A clamp disposed on the carrier 50 may also hold the spring 130 and spacer 62 in place. In some embodiments, spacer 162 comprises a flat piece of spring steel that can be replaced as needed or desired. In another embodiment, layers of spring steel may be joined to one another.

In the embodiment shown in fig. 14, a plurality of deflection plates 130 made of spring steel are combined to provide the desired assist spring force Fs. In the illustrated embodiment, the primary coil spring 40 has a spring rate of 91 lbs/inch and the secondary springs include 10 half-inch wide strips 130 of 3 mil thick spring steel. The half inch length of each flap deflects within a space of about 0.3 inches between the carrier 50 and the mount 68. The mounts are preferably incorporated into the frame 166. in the illustrated embodiment, the frame 166 has an overall width of about 0.66 inches, a length of about 2.3 inches, and a height of about 0.665 inches.

The 0.66 inch frame width and selected spring rate in the embodiment of fig. 14 approximates the spacing between the strings in a typical electric bass guitar and the desired force of the example bass guitar strings. Thus, with additional reference to fig. 15, in a preferred embodiment, a plurality of tensioning devices 160 may be mounted side-by-side on the headstock 168 of a bass guitar 170, with each tensioning device 160 dedicated to providing tension to a respective musical string 32. One end of the string 32 is secured to a bridge 172 that is supported on a body 174 of the guitar 170. The other end of the string 32 is attached to a respective one of the tension devices 160.

In the embodiments discussed above in connection with fig. 12-14, the spring plate is rigidly connected to the mount and the carrier, and is therefore considered a solid state system in which the components are not movable relative to each other. As such, there is little or no external friction. In addition, even if the tension device is exposed to external elements, such as dust and dirt, such elements do not substantially affect the spring function. It should be understood that embodiments employing other types of springs, including coil springs, rod springs, etc., may be configured such that the springs are rigidly connected to the mount and the carrier.

Referring next to fig. 16, in another embodiment of the tension device 180, a spring steel plate 190 is secured to the carrier 50 at the middle of the plate. The spring steel sheet 190 is deflected so that the outer end of the sheet is disposed generally parallel to the side mount wall 192 of the tension device 180 and is held securely in place by the mount 68. In another embodiment, the outer ends of the stack of sheets 190 may not be held in place by a mount.

With additional reference to fig. 17, a tension device 180 similar to the embodiment of fig. 16 employs a plurality of spring steel plates 190 mounted to the carrier 50 such that a space exists between each spring plate 190. Each flap is deflected on either side of the carrier 50 and the end of each spring steel flap 190 is placed against a seating wall 192 of a frame 194 with adjacent flaps 190 at least partially overlapping one another. Mount 68 may secure sheet 190 to mount wall 192. Each deflection plate exerts a laterally directed force on each side of the carrier 50 and the forces exerted by the plates are combined into a secondary force Fs. Each tab 190 may be secured to carrier 50 by being disposed below a bolt 196, which bolt 196 extends laterally over the respective tab 190 and deflects a middle portion of the associated tab. In further embodiments, each sheet may be rigidly attached to a respective fastener.

As mentioned above, embodiments of the tension device having features as described herein may be incorporated into a stringed instrument, such as a guitar. Embodiments may function and be placed as a bridge for a guitar or other stringed musical instrument. In other embodiments, a constant tension device as discussed herein may be placed on the head of a guitar (electric or acoustic), violin, cello, or other stringed instrument, thereby keeping the components spaced from the body of the instrument. It is noted that suitable stringed instruments for incorporating a tension device as discussed herein also include pianos, mandolins, guitars and other musical instruments.

"Sent" is the logarithmic unit of measure used for the interval. More specifically, monster is 1/100 of the difference in frequency from one note to the next in a 12-note chromatic scale. There are twelve notes in this scale at each octave, and each octave doubles the frequency, so that 1200 senters doubles the frequency. Thus, one senter is exactly equal to 2 for a given frequency^Λ(1/1200) times. Since the frequency is proportional to the square root of the tension, one is also equal to 2 from one tension value to a tension value off one^Λ((1/1200)*2)＝2^ΛThe tension of (1/600) is varied. 2^ (l/600) -l ^ 1/865 (0.001156). Therefore, each tension change by 1/865(0.001156) corresponds to a one-forest frequency difference. Similarly, each change in tension by 1/86(0.01156) is equivalent to a ten-cent difference in frequency, and each change in tension by 1/173(0.00578) is equivalent to a five-cent difference in frequency.

In one embodiment, the operating range of a tension device configured for use with a stringed instrument is selected to correspond to a frequency change of ten cents per travel of 1mm or less. In another embodiment, the operating range of the tension device is selected to correspond to a frequency change of pentant or less per 1mm of travel. The actual length of the operating range may vary, but in some embodiments is up to about 1mm of travel. In other embodiments, the operating range is up to about 1-1.5mm of travel. In a further embodiment, the operating range is up to about 2mm of travel.

Referring again to fig. 6 and table 3, in one embodiment, the 10 ° range from α ═ 5 ° to α ═ 4 ° corresponds to a total distance of displacement of 0.175 inches and an average spring rate of 1.37 pounds per inch, therefore, the change in tension from one side of this range to the other is 0.24 pounds, which is a change in tension of 0.24 pounds per 180 pounds 0.001332, which corresponds to about 1.15 cents, which is well within the desired range, and within a range that is not audibly detectable by the human ear.

To determine the maximum desired tension change to define a desired operating range, for example, a 10 Sent operating range, the tension of the string is multiplied by the value of the 10 Sent change frequency. For example, for a guitar string designed to be at a tension of about 10 pounds, the change in tension corresponding to the ten-tex frequency is calculated as 10 pounds (01156) to 0.12 pounds.

It will be appreciated that the components of any of the embodiments discussed above (and also including embodiments not explicitly discussed above, but which include features that are combined to form other embodiments employing the principles discussed herein) may be selected so as to construct a tension device having an operating range suitable for stringed musical instruments.

The embodiments discussed above have disclosed arrangements with a great deal of particularity. This has provided a good context for disclosing and discussing the subject matter of the present invention. However, it is to be understood that other embodiments may employ different specific structural shapes and interactions.

Although the inventive subject matter has been disclosed in the context of certain preferred or illustrated embodiments and examples, it will be understood by those skilled in the art that the inventive subject matter extends beyond the specifically disclosed embodiments to other alternative embodiments and/or uses of the invention and obvious modifications and equivalents thereof. In addition, while several variations of the disclosed embodiments have been shown and described in detail, other modifications, which are within the scope of the inventive subject matter, will be readily apparent to those of skill in the art based upon this disclosure. It is also contemplated that various combinations or sub-combinations of the specific features and aspects of the disclosed embodiments may be made and still fall within the scope of the inventive subject matter. Thus, it should be understood that various features and aspects of the disclosed embodiments can be combined with or substituted for one another in order to form varying modes of the disclosed subject matter. It is therefore intended that the scope of the inventive subject matter disclosed herein should not be limited by the particular disclosed embodiments described above, but should be determined only by a fair reading of the claims that follow.

Claims

1. A tension device comprising:

a primary spring attached to a carrier so as to exert a primary spring force directed along an axis, the primary spring force applied to the carrier varying as a primary spring rate function as the carrier moves along the axis relative to the primary spring;

a wire or string attached to the carrier and extending along the axis such that a net axial force applied to the carrier is applied to the wire or string; and

a secondary spring having a first end attached to the carrier for applying a secondary spring force to the carrier, the secondary spring force directed transverse to the axis and having an axial component applied to the carrier in a direction along the axis, the secondary spring force configured such that the axial component of the secondary spring force varies as a secondary spring rate function as the carrier moves along the axis relative to the primary spring;

wherein the net axial force applied to the carrier comprises the sum of the axial components of the primary and secondary spring forces, and

wherein the secondary spring is selected to approximate a linear change in the primary spring force as the primary spring moves linearly, and the secondary spring force changes such that a rate of change of the axial component of the secondary spring force approximately cancels a rate of change of the primary spring force.

2. A tension device as in claim 1, wherein the second end of the secondary spring is fixed and a secondary spring angle is defined between a line orthogonal to the axis and a line of action of the secondary spring, and wherein the carrier has an operating range defined as a distance along the axis between opposing first and second axial positions, the carrier being between the first and second axial positions.

3. A tension device as recited in claim 2, further comprising a first stop at the first axial position of the operating range, the first stop preventing the carrier from moving beyond the first axial position in a first direction.

4. A tensioning device as defined in claim 3, further comprising a second stop at the second axial position of the operating range, the second stop preventing the carrier from moving beyond the second axial position in a second direction.

5. A tension device as in claim 2, wherein the operating range corresponds to up to 10 ° of change in the secondary spring angle.

6. A tension device as in claim 5, wherein the operating range is defined within a range in which the secondary spring angle is between ± 5 °.

7. A tension device as in claim 1, wherein the secondary spring comprises a pair of springs acting on opposite sides of the carrier, the second end of the secondary spring being fixed.

8. A tension device as in claim 7, wherein the secondary spring is rigidly connected to the carrier and a fixed secondary spring mount.

9. A tension device as recited in claim 8, wherein the secondary spring comprises a deflected flat sheet in compression.

10. A tension device as recited in claim 9, comprising a plurality of said flat sheets spaced apart from one another.

11. A tension device as recited in claim 7, wherein the pair of springs includes a deflection rod.

12. A tension device as recited in claim 11, further comprising a connector between each deflection bar and the carrier.

13. A tension device as in claim 12, wherein the connector comprises an elongated rod.

14. A tension device as recited in claim 12, wherein the connector comprises a ball bearing.

15. A stringed musical instrument comprising a tension device as in claim 1, the wire or string comprising a musical string having a first end attached to the carrier and a fixed second end, wherein the secondary spring is selected such that the axial component of the secondary spring force varies as the secondary spring rate function as the carrier moves longitudinally along the axis, and the secondary spring rate function approximates and opposes the primary spring rate function such that the net axial force applied to the carrier remains within 1.2% of an initial tension force for every millimeter of longitudinal movement of the carrier.

16. A stringed musical instrument as in claim 15, wherein the secondary spring is selected such that the axial component of the secondary spring force varies as the carrier moves longitudinally along the axis according to the secondary spring rate function, and the secondary spring rate function approximates and opposes the primary spring rate function such that the change in the net axial force applied to the carrier remains within 0.6% of an initial tension force for every millimeter of longitudinal movement of the carrier.

17. A guitar comprising a tension device as in claim 1 mounted to one of a headstock and a bridge of the guitar, wherein a guitar string has a first end attached to the carrier and a second end attached to the other of the headstock and the bridge of the guitar, the tension in the guitar string being equal to the net axial force applied to the carrier.

18. A guitar as in claim 17, wherein the carrier is movable to a position where the guitar string is held at a desired tension, and wherein as the guitar string elongates, the axial force applied to the carrier by the primary spring decreases, and the axial component of the force applied to the carrier by the secondary spring in the direction the carrier moves as the string elongates increases.

19. A guitar as in claim 17, wherein the second end of the secondary spring is fixed and a secondary spring angle is defined between a line orthogonal to the axis and a line of action of the secondary spring, and wherein the carrier has an operating range defined as a distance along the axis corresponding to a change in secondary spring angle of up to 10 °, and wherein the primary spring has a primary spring rate and the secondary spring has an axial spring rate component that opposes the primary spring rate such that a change in tension in the guitar string within the operating range corresponds to a range of frequencies of 10 cents or less.

20. A tension device comprising:

a carrier configured to be movable along an axis;

a wire or string attached to the carrier and extending along the axis such that an axial force applied to the carrier is transmitted to the wire or string;

a target tension defined as a desired tension for the wire or string; and

a spring having a first end attached to the carrier and a second end attached to a spring mount, the spring mount being fixed such that the spring applies a spring force to the carrier, the spring angle being defined between a line normal to the axis and a line of action of the spring, the spring force being directed transverse to the axis and having an axial force component and an axial spring rate that is transmitted to the carrier in a direction along the axis;

wherein the spring is selected such that the axial force component is at the target tension when the spring angle is a zero stiffness angle at which an axial spring stiffness of the spring is zero.

21. A tension device as in claim 20, wherein the axial spring rate is one of negative or positive when the spring angle is greater than the zero rate angle and the axial spring rate is the other of negative or positive when the spring angle is less than the zero rate angle.